Various blends involving styrene-butadiene-styrene, styrene-isoprene-styrene, styrene-ethylene-butylene-styrene, ethyl vinyl acetate and their copolymers have been formulated as moisture-resistant barriers for hot melt coating on a substrate. Although coatings of these blends possess moisture resistance properties and are stable at temperatures up to 275.degree.-300.degree. F., they have relatively low bond strength and are hampered by a tack time up to about 5 minutes. Also, they do not provide ideal moisture-proof barriers when coated on non-woven substrates.
Low molecular weight polyethylene has also been considered for moisture resistant barriers; however, such coatings have low flexibility and are crisp and irritating to the touch. Accordingly, they are not suitable for articles of apparel or articles worn next to the skin, such as for example disposable diapers. In order to improve flexibility, formulations of polyethylene with elastomers or ethylene vinyl acetate have been proposed. Such blends are unsatisfactory since they require a high coat weight of 50-75 grams/meter.sup.2 on the substrate in order to retain moisture resistant properties, which in turn causes stiffness and thus defeats the purpose of formulation. Also, the amount of formulation required results in an objectionable bulky coating.
Accordingly, it is an object of this invention to overcome the above deficiencies while retaining the advantageous properties achieved by the combination of previous components.
Another object of this invention is to provide a continuous, pin-hole free coating to be used as a moisture-proof barrier on a substrate.
Still another object is to provide an efficient and economical method for preparing and applying a moisture-proof adhesive composition.
Yet another object is to provide a moisture-proof adhesive coating having excellent bonding properties and the ability to interlock with a wide variety of substrate materials.
These and other objects of the invention will become apparent from the following description and disclosure.